Device for producing thin films of mixed metal oxides from organic metal compounds on a substrate

ABSTRACT

In the device for producing thin films of metal oxides from organic metal compounds on a substrate, there is a truncated pyramidal hollow body (3) in an evacuable housing (1). Disposed concentrically with respect to the axis of symmetry (16) of the hollow body (3) in its base (7) are at least three furnaces (8) which have reception devices (9) for the metal compounds (10) to be evaporated. The reception devices (9) are provided with guide pipes (11) which project into the hollow interior of the hollow body (3) and are inclined towards its axis of symmetry (16). The casing (12) of the truncated pyramid merges into a pipe (13) above whose end there is disposed a heatable reception device (5) for the substrate (4). A gas feed pipe (6) terminates in the hollow interior [sic] of the hollow body (3) between the guide pipes (11) and the end of the pipe (13).

DESCRIPTION

The invention relates to a device for producing thin films of mixedmetal oxides from organic metal compounds on a substrate.

Because of their high critical temperature, the modern high-temperaturesuperconductors (HTSCs) consisting of mixtures of three and more metaloxides have aroused considerable interest. The HTSCs which are disposedas thin films on support substances (substrates) over a relatively largearea have acquired particular significance. Such films can be depositedon suitable substrates by vacuum evaporation, by means of sputteringprocesses, laser ablation, spin or spray coating, or the so-calledchemical vapor deposition (CVD) process. HTSC films of high quality canbe produced, in particular, by the CVD process. If narrow substrates,such as wires and filaments, are used, a side and back coating alsotakes place.

To carry out the chemical vapor deposition process, an evacuable devicewhich comprises three evaporators which are in communication with aheatable reception device for the substrate via a manifold has beendisclosed at the International Superconductivity Electronics Conference(ISEC '89) held on Jun. 12 and 13, 1989 in Tokyo [Extended Abstracts of1989 International Superconductivity Electronics Conference (ISEC '89),pages 425-428]. The organic metal compounds, such as, for example,β-diketone metal chelates of yttrium, barium and copper, are each heatedwith different intensities in the evaporators, the resultant vapor ofthese metal compounds is combined with an oxygen stream using argon ascarrier gas and pyrolyzed or oxidized at approximately 850° C., and theresultant mixed metal oxides are deposited on the substrate. Adisadvantage of this device is the expenditure on control technology forthe conveyor gas streams and the heating devices which are necessary forthe pipelines between the evaporators and the reception device in orderto prevent the condensation of the metal compounds there or to initiatea pyrolysis process prematurely. As a consequence of the dilutionresulting from the conveyor gas, the material consumption is high for adeposition rate of not more than 17 nm per minute. In addition, anappreciable portion of the metal compounds decomposes prematurely owingto the long conveyor paths.

It is here that the invention seeks to provide a remedy. The object isachieved by a device in which there is, in an evacuable housing, atruncated pyramidal hollow body

1. in which there are disposed, concentrically with its axis ofsymmetry,

a) at least three furnaces in the base of the hollow body which havereception devices for the metal compounds to be evaporated, whichreception devices are provided with guide pipes which project into thehollow interior of the hollow body and are inclined towards the axis ofsymmetry,

b) a pipe into which the casing of the truncated pyramid merges andabove whose end there is disposed a heatable reception device for thesubstrate, and

2. in whose hollow interior a gas feed pipe terminates between the guidepipes and the end of the pipe.

In addition, the furnaces may be symmetrically disposed around the axisof symmetry of the hollow body. A shutter may be disposed between thehollow body and the heatable reception device for the substrate. As gasfeed pipe, a plurality of nozzles or a nozzle ring may also be usedinstead of a single nozzle. The hollow body and the pipe may be providedwith a temperature-control device, i.e. for heating and/or cooling. Forthe purpose of thermal decoupling, baffle plates may be disposed betweenthe guide pipes.

The advantages achieved by the invention are essentially to be seen inthe omission of the conveyor gas and the simple compact construction ofthe device associated therewith. Furthermore, the material losses whichoccur in the known device owing to the severe dilution of the vaporswith the carrier gas do not apply. Premature pyrolysis of the metalcompounds is avoided by the omission of long lines. Deposition rates of130 nm per minute and over are achieved.

The invention is explained in greater detail below by reference to onlyone drawing depicting a method of embodiment.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows the device in perspective and in partial section.

Disposed in a housing 1 which can be evacuated via connecting piece 2 isa truncated pyramidal hollow body 3. Suitable truncated pyramidal hollowbodies are 3-sided to n-sided hollow bodies, including truncated conicalhollow bodies. Disposed concentrically with the axis of symmetry 16 ofthe hollow body 3 in the base 7 are at least three furnaces 8. Toproduce an HTSC mixed oxides containing more than three metals thenumber of furnaces 8 has to be increased accordingly.

Disposed in the furnaces 8 are reception devices 9 for the organic metalcompounds 10 to be evaporated. Said reception devices 9 are providedwith guide pipes 11 which project through the base 7 into the hollowinterior of the hollow body 3 and are inclined towards the axis symmetry16. As a result of the inclination of the guide pipes 11 towards theaxis of symmetry, the vapor clouds of the organic metal compoundsemerging from the guide pipes 11 overlap and are thoroughly mixed. Thefocussing and thorough mixing of the vapor clouds is assisted by theconical shape of the hollow body casing 12. The casing 12 merges into apipe 13 which is also disposed concentrically with the axis of symmetry16 and above whose end there is a heatable reception device 5 for thesubstrate 4. Opening into the hollow interior of the hollow body 3between the guide pipes 11 and the pipe 13 is a gas feed pipe 6 for theoxygen needed for the oxidation. To protect the substrate during thestart-up phase, a shutter (not shown) may be disposed between pipe 13and substrate 4. Baffle plates (not shown) may be disposed between theguide pipes 11 if a temperature equalization between the furnaces, whichare at different temperatures, has to be avoided. Hollow body 3 and pipe13 may be provided with a device 14 which serves for heating and/orcooling. Both the furnaces 8 and the reception devices 9 are providedwith temperature sensors 15, as is the reception device 5 for thesubstrate 4.

I claim:
 1. Device for producing thin films of mixed metal oxides fromorganic metal compounds on a substrate, characterized in that there is,in an evacuable housing (1), a truncated frustum shaped hollow body (3)formed from a casting (12), having a base (7) and an axis of symmetry(16), in which there are disposed, on a circumference of a circle thatis concentric with the axis of symmetry (16),a) at least three furnaces(8) in the base (7) of the hollow body which have reception devices (9)for the metal compounds (10) to be evaporated, which reception devices(9) are provided with guide pipes (11) which project into the hollowinterior of the hollow body (3) and are inclined towards the axis ofsymmetry (16), b) a confluence pipe (13), into which the truncatedfrustum hollow body merges, having a first and second end, and abovewhose second end there is disposed a heatable reception device (5) forthe substrate (4), andin the interior of the frustum shaped hollow body,a gas feed pipe terminates between the guide pipe (11) and the first endof the confluence pipe (13).
 2. Device according to claim 1,characterized in that the furnaces (8) are disposed symmetrically on acircumference of a circle that is concentric with respect to the axis ofsymmetry (16) of the hollow body (3).
 3. Device according to one ofclaims 1 or 2, characterized in that a shutter is disposed between thehollow body (3) and the heated reception device (5) for the substrate(4).
 4. Device according to claim 1, characterized in that the gas feedpipe (6) comprises a nozzle ring.
 5. Device according to claim 1,characterized in that the hollow body (3) and the pipe (13) are providedwith a temperature-control device (14).
 6. Device according to one ofclaim 1 to 5, characterized in that baffle plates are disposed betweenthe guide pipes (11).
 7. Device according to claim 2, characterized inthat the gas feed pipe (6) comprises a nozzle ring.
 8. Device accordingto claim 2, characterized in that the hollow body (3) and the confluencepipe (13) are provided with a temperature-control device (14).
 9. Deviceaccording to claim 2, characterized in that baffle plates are disposedbetween the guide pipes (11).
 10. Device according to claim 3,characterized in that the gas feed pipe (6) comprises a nozzle ring. 11.Device according to claim 3, characterized in that the hollow body (3)and the confluence pipe (13) are provided with a temperature-controldevice (14).
 12. Device according to claim 3, characterized in thatbaffle plates are disposed between the guide pipes (11).
 13. Deviceaccording to claim 4, characterized in that the hollow body (3) and theconfluence pipe (13) are provided with a temperature-control device(14).
 14. Device according to claim 4, characterized in that baffleplates are disposed between the guide pipes (11).
 15. Device accordingto claim 5, characterized in that baffle plates are disposed between theguide pipes (11).